1. Technical Field
The present invention relates to a zoom lens suited for electronic cameras such as a digital camera, a video camera, a broadcasting camera, a movie camera, a surveillance camera, and the like, and to an imaging apparatus including the zoom lens.
2. Description of the Related Art
As broadcasting cameras and movie cameras are easily affected by changes in angle of view by focusing, a zoom lens of a four-group configuration, which corresponds to such cameras, usually applies a focus system in which a first lens group is composed of a first-a lens group having negative refractive power, a first-b lens group having positive refractive power, and a first-c lens group having positive refractive power; and only the first-b lens group is moved. Examples of such zoom lenses include those disclosed in Japanese Unexamined Patent Publication No. 9 (1997)-015501, Japanese Unexamined Patent Publication No. 10 (1998)-062686, and Japanese Unexamined Patent Publication No. 2009-042346, for example.
In such zoom lenses having a first lens group composed of three groups as described above, a zoom lens of a five-group configuration which achieves a higher zoom ratio is proposed in Japanese Unexamined Patent Publication No. 10 (1998)-031157.
Furthermore, cinema cameras in particular require the same or higher performance compared with an imaging lens for a HDTV (high definition television). An example of a zoom lens which meets such a requirement is disclosed in Japanese Unexamined Patent Publication No. 2004-309761, for example.